The purpose of the study is to compare the early effects of two anti-glaucoma eye drops on eye pressure and inflammation of the eye using a microscope. One of the eye drops contains a commonly used preservative, benzalkonium chloride (BAK), while the other is free of this preservative, instead it utilises a new ionic buffer system called SofZia. Prolonged use of BAK may be damaging to the eye surface and thus being investigated at a microscopic level in this study.